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[TheBoy]

Every mechanic I know blames CAN when they don't understand CAN 

This is as true as 30 years ago when every mechanic blames the engine ECU for everything.

There is nothing difficult about CANBUS from a diags perspective, its just its "new"* and mechanics^# distrust what they haven't grasped.


* New as in most car designs for the last 15+ years have used it almost exclusively

^# Term used in the loose sense, to cover the usual knuckle draggers found at all dealerships

[Migv6 le Frog Fan]

Its got a couple of gallons of diesel in there at the moment.  Typical.
Im actually confident I would get at least what I paid for it even if the engine is fooked. It will cost  lot more than that to buy another half decent one though.

Its not as simple as the fuel shutoff solenoid on the pump?

Cracked the injector pipes open and fuel is getting up to the injectors. 
Gut feeling suspects are - air leaking into fuel supply, which is known to cause havoc. Knackered pump, which almost certainly means the end of the car. Head gasket, which will probably be the same result as knackered pump. 
I will try to find out from tomorrow when I should have time to have a play.

[Marks DTM Calib]

Its got a couple of gallons of diesel in there at the moment.  Typical.
Im actually confident I would get at least what I paid for it even if the engine is fooked. It will cost  lot more than that to buy another half decent one though.

Its not as simple as the fuel shutoff solenoid on the pump?

Cracked the injector pipes open and fuel is getting up to the injectors. 
Gut feeling suspects are - air leaking into fuel supply, which is known to cause havoc. Knackered pump, which almost certainly means the end of the car. Head gasket, which will probably be the same result as knackered pump. 
I will try to find out from tomorrow when I should have time to have a play.

For awareness, you can still get fuel.to the rail with a knackered solenoid (as I discovered recently on a 1.6D VW engine).

However, there is no pressure behind it so it does  not crack the injectors (Bosch pump).

It's worth applying 12V direct to the solenoid to see if you can hear or feel it go click 

[Kevin Wood]

Every mechanic I know blames CAN when they don't understand CAN 

This is as true as 30 years ago when every mechanic blames the engine ECU for everything.

There is nothing difficult about CANBUS from a diags perspective, its just its "new"* and mechanics^# distrust what they haven't grasped.


* New as in most car designs for the last 15+ years have used it almost exclusively

^# Term used in the loose sense, to cover the usual knuckle draggers found at all dealerships

I got given the task of developing a CAN module to drive a Ford Sierra rear light cluster for one of my A level electronics practicals so it's been around for at least 30 years, although it had a very slow start.

[Doctor Gollum]

Mercedes were an early adapter in the '91-'98 S Class with more and more complexity* in subsequent cars...

* this is actually an achievement as the W140 is stupidly over done

Jesting aside, is there a decent, straightforward book about CAN in order to get a better understanding of how it works?

[Migv6 le Frog Fan]

Its got a couple of gallons of diesel in there at the moment.  Typical.
Im actually confident I would get at least what I paid for it even if the engine is fooked. It will cost  lot more than that to buy another half decent one though.

Its not as simple as the fuel shutoff solenoid on the pump?

Cracked the injector pipes open and fuel is getting up to the injectors. 
Gut feeling suspects are - air leaking into fuel supply, which is known to cause havoc. Knackered pump, which almost certainly means the end of the car. Head gasket, which will probably be the same result as knackered pump. 
I will try to find out from tomorrow when I should have time to have a play.

For awareness, you can still get fuel.to the rail with a knackered solenoid (as I discovered recently on a 1.6D VW engine).

However, there is no pressure behind it so it does  not crack the injectors (Bosch pump).

It's worth applying 12V direct to the solenoid to see if you can hear or feel it go click 

Will need to check, but I don't think there is a solenoid or anything else electrical connected to the pump. I think its all mechanical.

[Marks DTM Calib]

Its got a couple of gallons of diesel in there at the moment.  Typical.
Im actually confident I would get at least what I paid for it even if the engine is fooked. It will cost  lot more than that to buy another half decent one though.

Its not as simple as the fuel shutoff solenoid on the pump?

Cracked the injector pipes open and fuel is getting up to the injectors. 
Gut feeling suspects are - air leaking into fuel supply, which is known to cause havoc. Knackered pump, which almost certainly means the end of the car. Head gasket, which will probably be the same result as knackered pump. 
I will try to find out from tomorrow when I should have time to have a play.

For awareness, you can still get fuel.to the rail with a knackered solenoid (as I discovered recently on a 1.6D VW engine).

However, there is no pressure behind it so it does  not crack the injectors (Bosch pump).

It's worth applying 12V direct to the solenoid to see if you can hear or feel it go click 

Will need to check, but I don't think there is a solenoid or anything else electrical connected to the pump. I think its all mechanical.

A quick check suggests its vac operated (the Merc designers have a constant love of steam age vac operated setups for some reason). So check your vac connections

[Migv6 le Frog Fan]

Will do, thanks.

Apologies to DG for thread hijack. 

[Doctor Gollum]

Just a quick update, finally got around to checking for codes and the voltages.

Cleaned the MAF sensor... it was quite sooty and ran the diagnostics again, took several attempts with the ignition on, off and running, but eventually got some sense out of the engine ecu. Reset it and now no EML

Battery/alternator checked out and on the OK side of inconclusive. Load applied was heated rear screen, headlights + main beam and blower on full.

Battery ign off, 14v.
Battery ign off load, dropped to 12.4v.
Cranking minimum, split second 10.39v.
Idle no load 13.99v.
Fast idle no load 14.08v
Idle load 13.8v
Fast idle load 14.08v

All perfectly OK, if a smidge low at fast idle.

Battery was brand new, around Easter iirc.

Touch wood, no further fuel pump issues either.